Figure 7.

Peptide phosphorylation activity in barley aleurone extract. A, Microsomal (pellet) and soluble (supernatant) fractions were prepared and their kinase activity assessed using 25 μm substrate peptides or histone. Assays were carried out in the presence of 50 μm CaCl₂ (+Ca) or 1 mm EGTA (−Ca). B, A range of syntide-2 concentrations was used on the soluble fraction in assays containing 50 μm CaCl₂, and the level of ³²P incorporation into the peptide during the initial 2 min of reaction was calculated. The reaction rate was linear over this time period. The results are the mean ± se of two experiments, with two replicates per experiment.